This invention relates generally to watt-hour meter covers and more particularly to watt-hour meter covers featuring enhanced access to and reliability in the operator interactive controls and displays of the meter.
The importance of interactive communication in energy consumption metering is recognized. For example, U.S. Pat. No. 4,638,314 to Keller discloses a remotely-read energy meter to which an electronics package has been added, the package includes a thin annular printed circuit board mounted for support on an annular adapter ring and disposed in surrounding relation to the annular watt-hour meter. Electrical components mounted on the printed circuit board provide an electronic read-out circuit for a pulse initiator, and further provide the transponder electronics for effecting bidirectional communication between the watt-hour meter and a remote location.
U.S. Pat. No. 4,783,623 to Edwards et al. discloses a device for converting standard electric meters to programmable interactive meters. The device includes a circuit for measuring energy use and is designed for installation below the rotating disc of a standard meter.
In response to the need for interactive communication, modern electric energy meters are equipped with operator interactive controls and readouts. A reset switch which is mechanically activated through hardware mounted to and passing through the face of the meter cover is typically present to enable resetting of the meter after energy consumption has been recorded. An LED indicator for calibration purposes pulses in relation to the power being measured. An infrared (IR) emitter/detector operates to bidirectionally exchange data and control commands with utility personnel and/or electronic data handling devices through an optical communication port mounted on the face of the meter. Communication between the fixed IR emitter/detector and the portable reader/programmer occurs through the transparent cover of the meter.
Problems are encountered in the design of the present systems. One problem arises since reset switch hardware normally has metal parts. Consequently, it is an entry point for electrostatic discharge (ESD) which can damage circuit components of the printed circuit board of the register. The IR emitter/detector has adequate power and sensitivity to operate only within very restricted ranges, alignment, and ambient light conditions. One solution to this problem has been to increase the distance between the register face and the meter cover face to reduce the incidence of ESD damage through the metallic hardware. This has made optical communication less reliable due to increased distance and greater exposure to interfering ambient light, mandating the use of specially designed meter covers to provide the necessary accuracy of cover to register spacing and precise alignment of the optical communication port with the emitter/detector to assure reliable operation over the full range of assembly tolerances and other manufacturing and service variables.
Improvement of signal transmissions in photo coupling devices has been a subject of some interest. U.S. Pat. No. 4,712,017 to Kamasaki shows a photo coupler device which comprises a light emitting element and a light receiving element made of a four layer structure of PNPN conductivity wherein a portion of the light receiving element through which the light enters does not contribute to its operation is covered with a light reflecting membrane. Various configurations facilitating interactive communication in energy consumption meters have been proposed. U.S. Pat. No. 4,298,839 to Johnston is an example of an electric energy meter having a programmable time base measuring system. A radiation sensitive external data interface receives and transmits data through a transparent communications window of the meter cover. The cover is provided with accurately spaced conical recesses which mate with projections on the programmer/reader. A radiation shielding baffle is mounted in the meter housing enclosed by the cover.
U.S. Pat. No. 4,584,527 to Amigo discloses a watt-hour metering system including a meter enclosed in a transparent cover and having an electronic register with a multichannel infrared responsive I/O port in a portable electronic programmer/reader having a complimentary infrared data I/O port. Inside the cover, the meter includes a pivoting shutter having a pair of magnets affixed thereto and held by gravity in a position to shield at least one channel of the I/O from radiation entering the cover. An activating magnet is affixed to the programmer/reader such that when the programmer/reader is placed against the meter cover, magnetic flux is coupled to the shutter magnets to cause the shutter to pivot and permit the transmission of infrared radiation. Alternatively, a shutter is pivotally secured to the cover and manually operable from outside the cover to selectively permit and prevent transmission of radiation.
U.S. Pat. No. 4,491,793 to Germer et al discloses a meter cover mounted receptacle and attachable magnetic coupler incorporating optical communication devices for communicating with electric circuitry housed within the meter cover. An umbilical cable enables an infrared emitter and detector to be assembled to the inside face of the meter cover directly inside the optical port hardware, thus controlling distance, alignment and ambient light.
Significant advantages in tooling cost and product lead time may be realized if it is possible to update meters using their existing glass or plastic covers. Certain designs presently in manufacture seek to improve upon the lack of manufacturing latitude imposed by the factors discussed above. One design, available from Landis & Gyr Metering, Inc. as PDR-A.TM., uses an electrically insulated reset switch to prevent entry of electrostatic discharge and thereby significantly reduces the cover-to-register space and thus the optical communication distance. This design, however, still requires a specially designed plastic cover to maintain the minimum spacing requirement and to provide the fine detail necessary to integrate the optical port into the end of the cover. Moreover, the insulating materials used in the reset switch do not have sufficient rigidity to facilitate an adjustment feature required to accommodate existing covers.
The design shown in Germer et al using an umbilical cable allows the cover depth to be varied by the designer as required to accommodate reset hardware or utilize existing cover designs without concern for optical communication reliability. The umbilical cable from the register to the optical port in the meter cover, however provides a solution that is awkward to handle and assemble, making access to the meter face difficult, and is relatively expensive to manufacture due to the number of additional components.
Consequently, there remains a need for an optical port design which efficiently transmits optical signals and yet offers simple assembly, ease of service, ruggedness and accommodates other meter design considerations. Most advantageously, such an optical port would be readily retrofitted to existing covers to preserve the investment in such.
Meters are commonly equipped with test mode switches which enable the meter operator to determine whether the meter is functioning properly or is in need of service. Commonly, these switches are accessed by removing the cover of the meter. It often occurs that, after testing the meter, the operator neglects to disengage the test mode switch. Because the meter is left in the test mode it does not record energy consumption. There is a need for test hardware design that addresses this problem.
With respect to other features of modern meters, it has been recognized that access to the meter battery and scroll and reset switches without the necessity of removing the meter cover is advantageous. Further, external access to the battery and switch actuators should be limited to prevent tampering. In this regard, various designs for switch actuators have been proposed. For example, U.S. Pat. No. 3,908,166 to Shackford discloses a watt-hour meter cover mounted rotary reset actuator incorporating a combination key operated, tamper resistant security lock and a rotary motion limiting device preventing application of excessive torque.
U.S. Pat. No. 4,074,192 to Hart discloses an external manual mechanism for resetting a cumulative demand register. The mechanism can be simply locked and unlocked for periodic use and may be applied to cumulative demand registers on watt-hour meters. A plunger with an arm pushes the reset crank. The mechanism is spring-biased in the disengaged mode.
U.S. Pat. No. 4,188,575 to Palmer et al discloses a meter cover mechanism incorporating a combination key operated tamper resistant security lock and externally controllable meter reset actuator and a meter access hatch. The reset switch is contacted by an actuator arm if the key is turned in the proper direction with the hatch closed. Access to the programmer probe is provided when the hatch is opened. Insertion of a battery replacement tool into the open hatch is suggested.
U.S. Pat. No. 4,602,211 to Losapio et al discloses an electronic demand register for an electric meter including a plurality of push button controls for controlling material displayed or a mode of operation of the demand register. A lockable switch actuator includes an actuating paddle within a cover or housing of the meter which, when unlocked, can be rotated into alignment with a selected one of the push button controls and then pushed inward to actuate the selected push button control.
Efforts have also been directed to providing restricted access hatches. U.S. Pat. No. 4,688,146 to Newmark et al is exemplary. A three piece molded plastic enclosure for service entry into apparatuses such as meters, fuses, circuit breakers, and switches is disclosed. The enclosure provides protection against adverse environmental conditions, while providing visual access to the components contained therein. The enclosure is tamper proof by virtue of a hinge arrangement formed between a stationary cover and a movable door. Once the door is assembled to the cover, the door cannot be easily removed without a separate tool.
Easy servicing of meter batteries is recognized as desirable. U.S. Pat. No. 4,791,362 to Philpot discloses a module meter assembly including a replaceable battery modules. An adaptor used with the meter assembly provides for retrofitting an improved modular structure on existing meters to permit upgrading of the functions performed by the existing meters. The modular device is designed for installation beneath the cover of the meter.
Further, some meters provide access to the meter battery without removing the meter cover. U.S. Pat. No. 4,075,561 to Stevens discloses an electrical apparatus enclosed within a housing containing a replaceable battery. Means for programming and for testing by means of connectable electrical contacts with an independent instrument are provided. The electrical apparatus is provided with a composite unit comprising a battery support and an electrical terminal connector which is arranged to cooperate with a single access port in the apparatus housing whereby routine servicing of battery replacements, programming and/or testing can be performed through a single port.
U.S. Pat. No. 4,297,635 to Stevens discloses an apparatus for retaining a replaceable battery comprised of a unitary structure having a chamber therein for receiving a battery and a resilient retaining means cooperating in the chamber with the battery provides a structure for easily replacing the battery. The apparatus is particularly adaptable to a programmable electrical watt-hour meter where a battery and programming connector in the watt-hour meter may be accessed through an access port in a housing of the watt-hour meter to replace the battery and service the watt-hour meter.
U.S. Pat. No. 4,713,679 to Losapio et al discloses a case including a hatch which permits removal and replacement of a battery without removing the case from the meter. In one embodiment the battery is installed in a battery clip on the face plate on the meter which is accessible through the hatch. An extra length of wires from the battery permits the battery and its miniconnectors to be withdrawn through the hatch for replacement thereof. In a second embodiment of the invention, the battery is captured in a durable hatch and is withdrawn from the meter by the action of opening hatch. In this embodiment, the hatch may be hinged or not hinged.
As demonstrated by the foregoing, the need for efficient access to the scrolling, resetting functions and routine maintenance aspects of watt-hour meters is understood. Until the present, this need has not been adequately addressed in a combined battery access hatch and locking reset and test switch assembly structure.